In this section we will discuss the possibilities of Spirit.Karma
when it comes to generating output from more complex - but still regular
- data structures. For simplicity we will use a std::vector<std::vector<int>>
as a poor man's matrix representation. But even if the data structure seems
to be very simple, the presented principles are applicable to more complex,
or custom data structures as well. The full source code of the example
discussed in this section can be found here: num_matrix.cpp.